In general, a wear resistant component or a sliding component is made of a cemented carbide which is based on WC, TaC or TiC, or an alloy corresponding to stellite which is based on Co-Cr-W. Such an alloy is prepared by binding hard particles of a carbide, a nitride and/or a carbonitride of W, Ta, Ti and/or Cr with an iron family metal such as Co, Fe or Ni through a well-known powder metallurgical method. More specifically, WC powder, TaC powder, Co powder and/or Ni powder are mixed with each other in accordance with a prescribed alloy composition and the mixed raw material powder is then die compacted or CIP-formed and the resulting compact is sintered.
In such a conventional method, however, the resulting product has its limitations regarding its shape in its dimensional accuracy since the compact is obtained by die compaction. Due to a uniaxial compacting pressure applied in the die compaction process, it is difficult to mold a material into a compact which is provided with holes or which has a plurality of surfaces along directions inclined against the pressing direction. Further, it is impossible to mold a material into a compact which is provided with grooves, thread grooves, knurls and the like in different directions with respect to a hole. If the compact has portions which are different in thickness from each other in excess of about 1.5 times, on the other hand, it is impossible to attain a homogeneous powder density and hence a difference is caused in the contraction during the sintering process, leading to a distortion of the component.
Although it is possible to mold a material into a compact having such a three-dimensional shape by CIP-forming, a sufficient accuracy cannot be attained by CIP-forming since the material is molded in a die of rubber. In order to obtain a component having a complex three-dimensional shape, a small hole or the like, therefore, it is necessary to secondarily work a sintered body which is first prepared in a simple shape.
In order to work a cemented carbide or an alloy of stellite which is extremely hard to work, however, it is necessary to grind the material with a diamond grindstone or apply an electric discharge machining. In particular, electric discharge machining is required for forming a small hole or the like. When a sintered body of a cemented carbide or a stellite alloy is subjected to electric discharge machining, however, small cracks or even breakage may be caused in or of the working surface by an external shock, whereby the entire component can break.
Although there is a well-known method of machine-working a compact which is obtained by die compaction or CIP forming into a complex shape and thereafter sintering the same, such a compact cannot attain a sufficient strength after the machine working. Thus, it is impossible to reduce the compact in thickness and work the same into a complex shape having a high dimensional accuracy, while breakage is easily caused by the machine work which reduces the strength of the sintered body.
Thus, it has been difficult to obtain a wear resistant component or a sliding component of a cemented carbide or a stellite alloy in a complex shape. As to a component which is machine-worked into a complex shape, on the other hand, it has been impossible to obtain the original strength that could be provided by starting material.